The present invention relates generally to an apparatus for monitoring burden distribution in a furnace, such as a shaft or blast furnace or the like. More particularly, the invention relates to an apparatus for monitoring the depth of an upper burden layer or layers and monitoring grain distribution in the burden layer.
As is well known, the shape of individual grains of the burden, and the depth and grain distribution of the upper burden layer or layers are very important factors in determining gas flow distribution and melting region configuration, which significantly influence the performance of the furnace. For instance, given identical conditions and material, furnace performance tends to be determined by burden distribution, i.e. the shape of individual grains of the burden and the depth and grain distribution in the upper burden layer or layers. Therefore, in order to keep the furnace performance at a desired level, it is necessary to maintain a proper burden distribution.
Maintaining a proper burden distribution requires that the burden distribution in the furnace be monitored. Conventionally, a sensor transversely movable across a burden layer measures the burden depth and inclination of the interface between the different burden layers or a vertically movable sensor measures the depth of the burden layer or layers. However, such conventional sensors measure only the depth of the burden layer or layers and cannot monitor grain distribution in the layer, which significantly influence gas flow distribution.
However, in the prior art, optical sensors have been used to monitor not only the depth of the burden layer but also the grain distribution of the burden. This kind of sensor comprises a light emitter which emits a laser beam or visual light beam toward the upper surface of the burden and an optical monitor directed toward the upper surface of the burden. The burden depth is measured by the difference in vertical height of the burden upper surface before and after supplying the burden.
Another conventional burden distribution measurement technique employs an arrangement of a stationary frame in the furnace, a plurality of first sensors monitoring burden depth and a plurality of second sensors monitoring grain distribution, the sensors fixedly mounted on the stationary frame.
These later systems have the advantage of monitoring not only the burden layer depth but also the grain distribution of the burden layer. However, in the case of optical sensors, measurement of the burden layer depth tends to be inaccurate due to irregularity of the upper surface of the burden layer when it is layed down. On the other hand, in the latter case, since the sensors are subject to relatively high furnace temperatures, the sensors have a relatively short service life and require frequent maintenance.